Telomeres are the ends of chromosomes. By capping the chromosomes, they are responsible for chromosomal integrity to prevent genomic instability1-3. Telomeres have been previously found at the nuclear edge4, at the nuclear periphery5, throughout the entire nucleus6, in non-Rabl association7, and in association with the nucleolus8. Similarly, the nuclear organization of chromosomes has been described as non-random9-13 or random14, based on two-dimensional (2D) imaging, three-dimensional (3D) reconstitution and mathematical modeling15. Organized territories of individual chromosomes have been observed in human 10-13, chicken16 and plant17. A regular nuclear organization has also been described for replication and transcription18-21. While all this points to a well-defined nuclear organization, studies on radiation-induced aberrations suggested a random chromosomal organization14.
At present, there is inexact knowledge about the 3D organization of either telomeres or chromosomes in interphase nuclei of normal, immortalized or tumor cells. However, this knowledge is of fundamental importance to the structural and functional organization of the normal nucleus and to the puzzle of genomic instability in tumor cells.